depolymerizable-olefinic-polymers-based-on-fused-ring-cyclooctene

Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers

The growing consumption of synthetic polymers and the accumulation of polymer waste have led to a pressing need for new routes to sustainable materials. ...

University of Akron

A promising solution to address the challenges in plastics sustainability is to replace current polymers with chemically recyclable ones that can depolymerize into their constituent monomers to enable the circular use of materials. Despite some progress, few depolymerizable polymers exhibit the desirable thermal stability and strong mechanical properties of traditional polymers. Here we report a series of chemically recyclable polymers that show excellent thermal stability (decomposition temperature >370 °C) and tunable mechanical properties. The polymers are formed through ring-opening metathesis polymerization of cyclooctene with a trans-cyclobutane installed at the 5 and 6 positions. The additional ring converts the non-depolymerizable polycyclooctene into a depolymerizable polymer by reducing the ring strain energy in the monomer (from 8.2 kcal mol in unsubstituted cyclooctene to 4.9 kcal mol in the fused ring). The fused-ring monomer enables a broad scope of functionalities to be incorporated, providing access to chemically recyclable elastomers and plastics that show promise as next-generation sustainable materials.

Olefin metathesis-based chemically recyclable polymers enabled by fused-ring monomers.

Degradable vinyl polymers by radical ring-opening polymerization are promising solutions to the challenges caused by non-degradable vinyl plastics. However, achieving even distributions of labile functional groups in the backbone of degradable vinyl polymers remains challenging. Herein, we report a photocatalytic approach to degradable vinyl random copolymers via radical ring-opening cascade copolymerization (rROCCP). The rROCCP of macrocyclic allylic sulfones and acrylates or acrylamides mediated by visible light at ambient temperature achieved near-unity comonomer reactivity ratios over the entire range of the feed compositions. Experimental and computational evidence revealed an unusual reversible inhibition of chain propagation by in situ generated sulfur dioxide (SO ), which was successfully overcome by reducing the solubility of SO . This study provides a powerful approach to degradable vinyl random copolymers with comparable material properties to non-degradable vinyl polymers.

Degradable Vinyl Random Copolymers via Photocontrolled Radical Ring-Opening Cascade Copolymerization.

Polymers that can be chemically recycled to their constituent monomers offer a promising solution to address the challenges in plastics sustainability through a circular use of materials. The design and development of monomers for next-generation chemically recyclable polymers require an understanding of the relationships between the structure of the monomers/polymers and the thermodynamics of polymerization/depolymerization. Here we investigate the structure-polymerization thermodynamics relationships of a series of cyclooctene monomers that contain an additional ring fused at the 5,6-positions, including -cyclobutane, -cyclopentane, and -five-membered cyclic acetals. The four- and five-membered rings -fused to cyclooctene reduce the ring strain energies of the monomer, and the enthalpy changes of polymerizations are found to be in the range of -2.1 to -3.3 kcal mol. Despite the narrow range of enthalpy changes, the ceiling temperatures at 1.0 M span from 330 to 680 °C, due to the low entropy changes, ranging from -2.7 to -5.0 cal mol K. Importantly, geminal substituents on the -five-membered cyclic acetal fused cyclooctenes are found to reduce the ceiling temperature by ∼300 °C, although they are not directly attached to the cyclooctene. The remote -disubstituent effect demonstrated here can be leveraged to promote depolymerization of the corresponding polymers and to tune their thermomechanical properties.

Understanding the Structure-Polymerization Thermodynamics Relationships of Fused-Ring Cyclooctenes for Developing Chemically Recyclable Polymers.

Chemical recycling to monomer (CRM) is a promising route for transitioning to a circular polymer economy. To develop new CRM systems with useful properties, it is important to understand the effects of monomer structure on polymerization/depolymerization behavior. In earlier work, this group demonstrated chemically recyclable polymers prepared by ring-opening metathesis polymerization of trans-cyclobutane fused cyclooctenes (tCBCO). Here, it is investigated how different substituents on cyclobutane impact the thermodynamics and thermal properties of tCBCO polymers. Introducing additional substituents to a cis-diester functionalized tCBCO is found to favor the conversion of polymerization; increased polymerization conversion is also observed when the cis-diester is isomerized into its trans counterpart. The effects of these structural features on the thermal properties are also studied. These findings can provide important insights into designing next-generation CRM polymers.

Article	Year
Olefin metathesis-based chemically recyclable polymers enabled by fused-ring monomers. Nature chemistry\| PubMed ID: 34294914	2021
Degradable Vinyl Random Copolymers via Photocontrolled Radical Ring-Opening Cascade Copolymerization. Angewandte Chemie (International ed. in English)\| PubMed ID: 34890493	2022
Understanding the Structure-Polymerization Thermodynamics Relationships of Fused-Ring Cyclooctenes for Developing Chemically Recyclable Polymers. Journal of the American Chemical Society\| PubMed ID: 34985870	2022
Regulating the Thermodynamics and Thermal Properties of Depolymerizable Polycyclooctenes through Substituent Effects. Macromolecular rapid communications\| PubMed ID: 35686515	2022

Devavrat Sathe

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